In many countries, the law requires motorists to move to a side of the road when an emergency vehicle with an operating siren approaches, as soon as the motorists are able to do so in a safe manner. Often, emergency vehicles are slowed while en route to a dispatched location by motor vehicles the operators of which do not respond to the approaching emergency vehicle for reasons which might include lack of hearing the siren (i.e. windows rolled up) or distractions such as a radio playing, talking on a cell phone or listening to a CD/DVD player.
Many systems and methods have been devised to alert motorists of an approaching emergency vehicle en route to a dispatched location.
U.S. Pat. No. RE 38,763 discloses a system and method for alerting a driver of a motor vehicle of the approach of an emergency vehicle in an emergency state, comprising a transmitter in the emergency vehicle which produces and transmits a radio frequency signal having a unique audio encoded data signature modulated thereon when the emergency vehicle is in an emergency status, a receiver in a motor vehicle which receives the radio frequency signal, demodulates and decodes the radio frequency signal and produces a voltage output when the data signature is present; and an alarm producing device which produces an alarm in response to the voltage output warning the driver of the motor vehicle of the approach of the emergency vehicle.
U.S. Pat. No. 6,822,580 discloses a warning system for alerting the driver of a private vehicle that an emergency vehicle is approaching. The system includes a receiver and a display panel mounted in the private vehicle, and at least two infrared receivers mounted on the private vehicle. The display panel mounted in the private vehicle including indicating devices that allow the driver of the private vehicle to know of the approaching emergency vehicle as well as the direction to move in order to yield the right of way to an approaching emergency vehicle; and a warning signal emitting device mounted in the emergency vehicle, the warning signal emitting device providing signals that allow the components of the emergency vehicle warning system mounted in the private vehicle to know that the approaching vehicle is an emergency vehicle.
U.S. Pat. No. 6,252,521 discloses an emergency vehicle alert system that includes transmitter units mountable within emergency vehicles and receiver units mountable within civilian vehicles. The transmitter units and the receiver units via a mechanism within each receiver unit that provides each civilian driver with an indicator of the distance between his/her civilian vehicle and the emergency vehicle.
U.S. Pat. No. 5,959,551 discloses an invention for use in warning motorist, especially those who are hearing impaired, of an approaching emergency vehicle. The invention comprises a transmitter which is installed into an emergency vehicle and activated upon an emergency run. A low frequency signal is sent out over the emergency vehicles original equipment antenna system and is picked up by motorist having a receiver unit mounted to their dash panel. The signal is processed into visual and audio warnings whenever a transmitting emergency vehicle is within close proximity to the receiving vehicle. The receiver is on full time when the motor vehicle is in operation thereby allowing suitable response time for motorist to take appropriate action in yielding to the emergency vehicle. The transmitter does however have an on/off switch as well as a visual and audio means for monitoring the transmitted signal.
U.S. Pat. No. 6,160,493 discloses a low-cost and reliable radio warning system that alerts system users of potential hazardous conditions is disclosed. The system makes use of a transmitter and at least one receiver. The transmitter generates and transmits a radio warning signal that carries a digital data sequence that includes information concerning a particular potential hazardous condition from which the transmission was initiated, such as an approaching ambulance, fire truck, bus, train, or the like. Other information, such as GPS coordinates, may also be included. Through the use of digital encoding techniques, the system's susceptibility to false alarms or “false triggers” is minimized. The radio warning signal is transmitted in burst transmissions and may use a number of signaling techniques, including spread spectrum transmission, which increases system reliability and performance even in the presence of interference or multipath distortion. System users are equipped with a receiver that receives the radio warning signal and interprets the digital data and information carried by the warning signal. The receiver alerts the system user who has received the radio warning signal of the potential hazardous condition through the use of an audible, visual or tactile alarm.
U.S. Pat. No. 7,236,101 discloses a warning system for making known the presence of an emergency vehicle. A transmitter is mounted in an emergency vehicle that outputs a digital UHF/LMS signal that is detectable within a range. A receiver responds to the digital UHF/LMS signal from the transmitter and is mounted, most preferably to a dashboard of a motor vehicle. The receiver detects from the digital signal the type of emergency vehicle from which the digital signal is originating. In one embodiment the digital signal also includes a unique identifier for the transmitter rather than simply a generic discipline identifier such as police, fire, emergency etc. A visual indicator mounted to the motor vehicle is activated in response to the digital signal from the transmitter to warn a motorist in the motor vehicle of a presence of the emergency vehicle within the range of the transmitter and to warn the transmitting vehicle of the presence of other emergency vehicles within receiving range.